The detection of neutrons is important in many applications ranging from basic materials research to national security. Neutrons have no electrical charge and can penetrate far deeper into matter than x-rays, gamma rays, charged particles, or visible light. For this reason, neutrons offer certain advantages for the detection of radioactive materials.
The detection of neutrons in matter is primarily based on indirect methods. Neutrons can be detected through nuclear reactions involving an interaction material whereby the neutron is absorbed via electromagnetic, charged, neutral, and/or fission means, or converted/scattered via elastic and/or inelastic means. This results in a prompt nuclear reaction—the products of which can include protons, alpha particles, gamma rays, fission fragments, etc. These reaction products can then be collected and recorded as indicative that one or more interaction events occurred. Known interaction materials effective in the detection process include helium-3, lithium-6, boron-10, boron-trifluoride (“BF-3”), and/or fissile uranium.
Various measurement results are of interest in neutron detection, including the location of the interaction, the time of the interaction, and the energy of the neutron involved in the interaction. Additional detector requirements may include the need for a large area, operability at high count rates, and/or reduced gamma ray background radiation.
Presently, gas proportional counters using helium-3 as the interaction material are the detector of choice in many neutron measurement systems. Helium-3 provides for stable and efficient neutron conversion. However, there is severe shortage of available helium-3, with some estimates indicating that the supply will last less than 30 years. Department of Energy facilities utilizing neutron detection technology, such as the Spallation Neutron Source (SNS) facility are especially concerned with the shortage of available helium-3, particularly in light of their need for large detection areas. Instruments at SNS, such as the Fine-Resolution Fermi Chopper Spectrometer (SEQUOIA) require greater than thirty square meters of detection area, as well as systems having high efficiency, high count-rate, and very low gamma background capabilities.
Another type interaction material is enriched boron, such as boron-10 (e.g., boron enriched beyond 20%), which has 72% the neutron cross section as helium-3. Indeed, use of boron-10 in lining detector surfaces is known in the art. Frequently, boron-10 lined proportional detector tubes are grouped in clusters, and have recently began exhibiting neutron efficiency characteristics similar to those of helium-3 detectors largely due to the increased surface area of boron-10 for detecting the neutron reactions. However, using clusters of boron-10 lined detector tubes is not suitable for position resolution, timing resolution, or count-rate requirements for most neutron scattering applications.
In light of the above, there presently exists a need in the art for a neutron detection system suitable for position resolution, timing resolution, and high count-rate operability. The present general inventive concept provides a solution in the form of individual pixel-cell chambers lined or combined with an interaction material, which will provide numerous advantages over the prior art in the areas of detector volume capability and required expenditures. It is noted that the present general inventive concept will accommodate a wide range of neutron measurement applications.